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From: Gao Xiang <gaoxiang25@huawei.com>
To: "Theodore Y. Ts'o" <tytso@mit.edu>, Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Eric Biggers <ebiggers@google.com>,
	linux-fscrypt@vger.kernel.org, linux-kernel@vger.kernel.org,
	Chao Yu <yuchao0@huawei.com>, Miao Xie <miaoxie@huawei.com>,
	weidu.du@huawei.com, Gao Xiang <gaoxiang25@huawei.com>
Subject: [RFC PATCH v2 2/2] fscrypt: enable RCU-walk path for .d_revalidate
Date: Mon, 10 Sep 2018 21:08:57 +0800	[thread overview]
Message-ID: <1536584937-16960-1-git-send-email-gaoxiang25@huawei.com> (raw)
In-Reply-To: <1536584468-15695-2-git-send-email-gaoxiang25@huawei.com>

This patch attempts to enable RCU-walk for fscrypt.
It looks harmless at glance and could have better
performance than do ref-walk only.

Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
---
change log v2:
	- READ_ONCE(dir->d_parent) -> READ_ONCE(dentry->d_parent)

 fs/crypto/crypto.c | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c
index b38c574..9bd21c0 100644
--- a/fs/crypto/crypto.c
+++ b/fs/crypto/crypto.c
@@ -319,20 +319,24 @@ static int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags)
 {
 	struct dentry *dir;
 	int dir_has_key, cached_with_key;
-
-	if (flags & LOOKUP_RCU)
-		return -ECHILD;
-
-	dir = dget_parent(dentry);
-	if (!IS_ENCRYPTED(d_inode(dir))) {
-		dput(dir);
+	struct inode *dir_inode;
+
+	rcu_read_lock();
+repeat:
+	dir = READ_ONCE(dentry->d_parent);
+	dir_inode = d_inode_rcu(dir);
+	if (!IS_ENCRYPTED(dir_inode)) {
+		rcu_read_unlock();
 		return 0;
 	}
+	dir_has_key = (dir_inode->i_crypt_info != NULL);
+	if (unlikely(READ_ONCE(dir->d_lockref.count) < 0 ||
+		READ_ONCE(dentry->d_parent) != dir))
+		goto repeat;
+	rcu_read_unlock();
 
 	cached_with_key = READ_ONCE(dentry->d_flags) &
 		DCACHE_ENCRYPTED_WITH_KEY;
-	dir_has_key = (d_inode(dir)->i_crypt_info != NULL);
-	dput(dir);
 
 	/*
 	 * If the dentry was cached without the key, and it is a
-- 
1.9.1

WARNING: multiple messages have this Message-ID (diff)
From: Gao Xiang <gaoxiang25@huawei.com>
To: "Theodore Y. Ts'o" <tytso@mit.edu>, Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Eric Biggers <ebiggers@google.com>,
	<linux-fscrypt@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	Chao Yu <yuchao0@huawei.com>, Miao Xie <miaoxie@huawei.com>,
	<weidu.du@huawei.com>, Gao Xiang <gaoxiang25@huawei.com>
Subject: [RFC PATCH v2 2/2] fscrypt: enable RCU-walk path for .d_revalidate
Date: Mon, 10 Sep 2018 21:08:57 +0800	[thread overview]
Message-ID: <1536584937-16960-1-git-send-email-gaoxiang25@huawei.com> (raw)
In-Reply-To: <1536584468-15695-2-git-send-email-gaoxiang25@huawei.com>

This patch attempts to enable RCU-walk for fscrypt.
It looks harmless at glance and could have better
performance than do ref-walk only.

Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
---
change log v2:
	- READ_ONCE(dir->d_parent) -> READ_ONCE(dentry->d_parent)

 fs/crypto/crypto.c | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c
index b38c574..9bd21c0 100644
--- a/fs/crypto/crypto.c
+++ b/fs/crypto/crypto.c
@@ -319,20 +319,24 @@ static int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags)
 {
 	struct dentry *dir;
 	int dir_has_key, cached_with_key;
-
-	if (flags & LOOKUP_RCU)
-		return -ECHILD;
-
-	dir = dget_parent(dentry);
-	if (!IS_ENCRYPTED(d_inode(dir))) {
-		dput(dir);
+	struct inode *dir_inode;
+
+	rcu_read_lock();
+repeat:
+	dir = READ_ONCE(dentry->d_parent);
+	dir_inode = d_inode_rcu(dir);
+	if (!IS_ENCRYPTED(dir_inode)) {
+		rcu_read_unlock();
 		return 0;
 	}
+	dir_has_key = (dir_inode->i_crypt_info != NULL);
+	if (unlikely(READ_ONCE(dir->d_lockref.count) < 0 ||
+		READ_ONCE(dentry->d_parent) != dir))
+		goto repeat;
+	rcu_read_unlock();
 
 	cached_with_key = READ_ONCE(dentry->d_flags) &
 		DCACHE_ENCRYPTED_WITH_KEY;
-	dir_has_key = (d_inode(dir)->i_crypt_info != NULL);
-	dput(dir);
 
 	/*
 	 * If the dentry was cached without the key, and it is a
-- 
1.9.1


  reply	other threads:[~2018-09-10 18:03 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-10 13:01 [RFC PATCH 1/2] fscrypt: remove d_lock on reading DCACHE_ENCRYPTED_WITH_KEY Gao Xiang
2018-09-10 13:01 ` Gao Xiang
2018-09-10 13:01 ` [RFC PATCH 2/2] fscrypt: enable RCU-walk path for .d_revalidate Gao Xiang
2018-09-10 13:01   ` Gao Xiang
2018-09-10 13:08   ` Gao Xiang [this message]
2018-09-10 13:08     ` [RFC PATCH v2 " Gao Xiang
2018-09-10 23:20     ` Eric Biggers
2018-09-11  5:29       ` Gao Xiang
2018-09-11  5:29         ` Gao Xiang
2018-11-06 12:20 [RFC PATCH v2 1/2] fscrypt: remove d_lock on reading DCACHE_ENCRYPTED_WITH_KEY Gao Xiang
2018-11-06 12:20 ` [RFC PATCH v2 2/2] fscrypt: enable RCU-walk path for .d_revalidate Gao Xiang
2018-11-06 12:20   ` Gao Xiang

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